Does any of this need a health warning should a hack try to write to objects (is it all threadsafe/sychronised - will it work)?

There is no thread safety but as long as each thread manipulate the data of its "own" AlbumObject, then there is no interference. If you interact with shared data, ensure you synchronize some how (by using the synchronized keyword or use atomic objects (see AtomicInteger and such)

I have added a section to the Sample scripts page which includes a link back here, probably easier than trawling through the forum in a few months time.